Mechanical filling of porous wood



April 1944' E. A. LEHMAN 2,345,941

MECHANICAL FILLING OF POROUS WOOD Filed Dec. 17, 1941 INVENTOR 506/? A. LEHMAN Patented Apr. 4, 1944 MECHANICAL-FILING or ronous woon Edgar A. Lehman, Mishawaka, Ind., assignor to The American Foundry Equipment Company, Mishawaka, Ind., a corporation of Delaware Application December 17, 1941, Serial No. 423,323

Claims. (01. 117-16) This invention relates to the mechanical mung of porous wood, preparatory to the application of a primer, paint, lacquer, or finishing coat thereto Certain woods commonly used for furniture, interior building trim and panelling, such as' oak, walnut, mahogany, hickory and similar valuable woods, present in their planed surfaces small and relatively minute pores, which is a. characteristic of the wood growth. It is necessary to fill these pores with a suitable filler before application of I the primer and finishing coat if the finished product isto possess the desired surface smoothness and finish.

These pores are commonly filled with an earth filler. The filler commonly used contains a suitable earthy body material generally of the silica group, such as a natural silica reduced to fine powder, and is usually white in color and is gen- A erally referred to as silex. The silex'powder is mixed with a suitable drier and a vehicle oil to permit application to the wood as by spraying, brushing or dipping. The vehicle employed is usually tung oil, linseed oil or a suitable resin, and the drier employed may be japan or boiled linseed oil. The silex powder is relatively inexpensive as measured by the area which it will coat, but the drier and vehicle constitute the most costly ingredients of the filler material. Since the filler is later dried, the drier and vehicle are largely lost through evaporation and therefore impart no important ingredient to the finished surface, but are added to the powdered material Thereafter the filler must be dried before a primer or other paint or lacquer coat can be applied to the wood surface. The drying can be effected by hanging the filled wood in a warm room for approximately twelve hours, or can be oven dried in approximately four hours.

The present method of filling porous wood as 4 above'described is expensive, laborious and time-- consuming. The valuable driers and vehicles are substantially all lost in drying without useful effect. Since the final finish of the wood depends to a large extent on the skill of the workman applying the filler, the finished s rface of otherwise fine wood is often inferior due lack of skill of the workman applying the filler. Furthermore, even though the pores are uniformly and fully filled with the liquid or pasty filler, the filler deposited in the pores of the wood shrinks upon drying due to the escape of the volatile components of the drier and vehicle so that the dried filler only partially fills the pores, leaving a small pinhole depression in the filled surface of the wood which to facilitate application of the filler to the wood.

After'the liquid filler has been applied to the wood, it is permittedto partially dry, which gen- 7 erally takes a few minutes, so that the woodsurproximately two square feet of wood surface per minute. The rag or moss shortly becomes saturated with the moist filler after a limited surface has been treated and is then not fitted for further use and is thrown away. Considerable quantitiesof filler are thus thrown away with the rag, burlap or moss applicator.

The woodworker must then clean off all excess filler with a fresh, clean rag, burlap or moss pad and by working diligently can clean from six to eight square feet per minute of wood surface.

is visible when the finished coat is applied. Furthermore, the shrinkage of the filler upon drying often causes the filler material in the pores to break looseifrom the wood surface surrounding the pores, so that the filler often drops out of the pores or causes chippin or cracking of the lacquer finish due to the failure of the bond between the filler and the wood.

It is an object of this invention improveupon present-known methods of filling the pores of wood, whereby the cost of the filling operation may be'substantially reduced and an improved filled wood product obtained.

Another object. of this invention is to provide an improved method of filling wood whereby a firmer and more tenacious bond between the filler material and the wood iseifected. o

Another object of this invention is to provide an improved method of filling the pores of valuhated.

Another object of this invention is to provide an improved method of filling the pores of valution;

able woods by mechanically calking the pores with a substantially dry filler material.

Another object of this invention is to provide as an article of manufacture a porous wood having the pores thereof calked with dry filler ma terial so as to present a firm and tenacious bond between the filler material and the wood and a substantially flush and smooth filled surface.

Other objects of this invention will become apparent as the disclosure proceeds.

Various other features and advantages of the invention will be apparent from the following particular description and from an inspection of the accompanying-drawing.

Although the novel features which are believe tobe characteristic of this invention will be particularly pointed out in the claims appended heretoythe invention itself, as to its objects and advantages and the manner in which it may be carried out, may be better understood by referring to the following description taken in connection with the accompanying drawing forming a part thereof, in which:

Fig. 1 is a plan view of a short section of porous .wood showing the pores therein which are to be filled with the filler material greatly magnified;

Fig. 2 is a cross-section of the porous wood to be treated in which the pores thereof are greatly I magnified to facilitate illustration;

Fig. 3 shows greatly magnified the hard balls or shot coated with dry filler material which are thrown at high velocity against the porous wood surface to effect calking of the pores thereof. one

ball being shown uncoated to facilitate illustra- Fig. 4 is a diagrammatic illustration of acentrifugal projector wheel preferably employed for firing the filler coated :balls or shot against the wood surface, which operate to. deposit the powdered filler material into the wood pores and calk the filler in the pores, completely filling the pores;

Fig. 5 is a magnified cross-sectional view of a fragmentary portion of the calked wood showing the relative size of the pores with respect to the calking balls employed in calking theporesf Fig. 6 is a plan view of the porous wood after the pores have been calked with the filler material, this view also showing a doctor blade or other wiping element positioned across the surface of the wood, which is employed to scrape off excess dry filler material deposited on the surface of the wood and not contained within the pores thereof; and.

Fig. 7 is a magnifiedcross-sectional view of the porous wood showing the pores thereof completely filled and calked with the dry filler material.

mixed with liquid driers, vehicles, or similar liquid material which heretofore have constituted an important part'oi' the liquid filler heretofore employed.

The dry powdered filler II is applied to the pores of the wood by bombarding the porous wood surface with hard balls or steel shot It of generally spherical form, which have been previously coated or mixed with the dry filler powder ll asiilustrated in Fig. 3. Clean round shot such as normally employed in blast cleaning operations may be used, but the surface of the shot should be clean and bright and free from rust or undesirable surface deposits which might otherwise discolor the wood.

It is important that the shot i0 which is selected have a diameter substantially greater than the size or diameter of the pores 2 in the surface 3 of the wood to be treated. The size of the shot l0 selected will therefore depend to a certain extent upon the size and shape of the pores in the wood to be treated. I have found that round steel shot which is (designated commercially as No. 18 mesh size is usually satisfactory for the treatment of most porous woods,

although steel shot as large as No. 12 mesh size and as small as -,No. 40 mesh size may be used on certain woods. No. 12 mesh size shot has a diameter such that it will be retained on a screen having-openings of .060 inch but will pass through a screen having openings of .065 inch; No. 18 mesh size shot will be retained on a screen having openings of'.040 inch but will pass through a screen having openings of .055 inch; while No. 40 mesh size shot will be retained on a screen having openings of .017 inch but will pass through a screen having openings of .019 inch. The larger No. 12 mesh size shot may be used on woods having very large pores while No. 40 mesh size shot may be used on woods having very small pores. Intermediate size shot, such as No. 18 mesh size for example, has been found to be satisfactory for most woods having average size pores. v

The shot I0 is mixed with the dry filler powder Ii in such proportions as to coat the surface of the shot with the filler material as illustrated in Fig. 3. ,Mihile some loose filler powder which Similar reference characters refer to similar parts throughout the several views of the drawing and the specification.

There is illustrated in Figs. 1 and 2 a piece of wood i having a planed surface 3 containing numerous minute pores 2 which are to be filled with my improved process in dry form and is not is not c ted on the balls will result during operatio it is desirable that an excess quantity of filler powder not be employed if the best results and ghost emcient operations are to be realized- The filler coated steel balls are fed into the center of a bladed centrifugal blasting wheel 4 which is rotated to develop a peripheral velocity of from 3,000 to 10,000 lineal feet per minute.

A satisfactory form of abrasive throwing wheel which may be employed is illustrated in Unger Pat. No. 2,162,139. Such wheels employ a control cage and impeller for directing the bombarding blast in the desired direction against the wood surface 3 to be treated. The blast is directed uniformly against the wood surface as illustrated in Fig. 4. The filler coated steel balls should be thrown with as high velocity as possible short of denting the wood surface. The velocity at which the hard balls can be thrown without denting the wood surface will vary with th hardness of the wood being treated but will generally fall within the velocity limits above stated.

The filler powder ii is driven into the pores 2 when the hard coated balls I. strike the wood surface}, the filler powder ii being left in the pores when the balls rebound or glance oil the surface. The impact force of the continuous stream of coated balls 10 quickly fills the pores with a hard compact mass ll' of filler material which firmly adheres to the surrounding minute walls of the pores. Since the hard balls III are many times larger than the mouth of the pores,

the balls do not enter the pores'during'the impact .but leave the top surface ll" of the calk filler ll substantially smooth and flush with the calked filler il' within the planed surface 3 of the wood.

Dry coloring material, such as pigments, dyes, or lakes, may be mixed with the filler powder II to stain the wood. surface and the filler alike to matchuniformly any stain that may be separately applied after the filling.

The pores 2 in the wood surface 3 may be filled mechanically by my improved process at almost any desired speed. For example, if the porous wood to be filled is inthe form of flat boards.or panels which can be carried alor g on a conveyor belt, the pores may be filled when evident.

After the pores 2 have been calked with the powdered filler material through the bombardment action of the shot, there is usually a small amount of dry filler powder which is scattered over the surface 3 of the wood and not contained in the pores.

moved by any convenient mechanical method,

such as wiping, brushing or scraping. Inthe cas of fiat wood pieces, such as boards or panels. the excess filler powder may be removed by running the wood under a doctor blade 8, as shown in Fig. 6. which serves to scrape oil? the excess material.

When the excess filler material has been scraped, brushed or wiped oif from the surface 3 it will be found that the pores 2 are uniformly filled with the filler material tightly'compacted and firmly bonded to the surrounding walls of the pores. The top surface ll" of the calked filler II in the pores is also flush with the wood surface 3 so that the filled wood surface is smooth and evenly filled. The filler powder Ii has b come compacted in the pores to the extentthat it is extremely hard and retains its compacted form without shrinkage as results when filler paints are employed.

time-consuming operations of padding, rubbing,

wiring and drying ofv the filler paint is entirely dispensed with. Only dry filler powder is used and the usual vehicles and driers heretofore used for filler paints are also dispensed with, thus greatly reducing the cost of the filler material per area of surface treated. The centrifugal abrasive throwing wheel can be driven by a motor of two to ten horsepower. The steel shot employed will last indefinitely and after being thrown The excess material is re- 35 Porous wood may filled by myimproved method at many times the speed and at a fraction of the cost of the hand filling methods commonly employed, and with thenresult that a filled wood product is produced which is substantially superior to any porous woods filled with filler paints by present methods. The finished product presents a more uniform filled surface, the filler material is more firmly bonded to the side 10 walls of the pores, the filler material is more firmly compacted and calked into the pores, the top surface-of the filler is uniformly coplanar with the planed surface of the wood, and the filler material thus applied will not shrink or contract, as here-. tofore occurs.

By mixing dry coloring material with the filler.

the calked filler ll' may be colored to correspond surface of the filled wood. The pigment powder also serves to dry-stain the planed surface of the wood so that a more uniform staining effect can 1 with the stain to be later applied to the planed be obtained by following the staining operation.

annexed claims, it will be understood that various omissions, substitutions and changes may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is:

1. The method of filling the surface pores of porous wood which includes, bombarding the porous wood surface with substantially spherical shot coated or mixedwith filler powder.

2. The method-of filling the sin-face pores of porous wood which includes, coating spherical shot with dry filler powder, and projecting said filler-coated shot agains'tthe porous wood surface 40 porous wood which includes, coating spherical shot with dry filler powder, and centrifugally proiecting said filler-coated shot against the porous wood surface to calk said filler in the surface pores.-

4. The method of filling the surface pores of porous .wood which includes, coating spherical 10,000 lineal feet per minute to calk said filler in the surface pores.

5/The method of filling the surface poresof bus wood which includes, selectingspherical not having a diameter substantially greater than the mouth of the surface pores' to be filled, coat- .By my improved method the expensive and ing said shot with dry filler powder, and centrifugally projecting said shot against the porous wood surface to deposit and hammer said filler into said surface pores.

6. The method of filling the surface pores of porous wood which includes, selecting spherical shot having a diameter substantially greater than the mouth of the surface pores to be filled, coating said shot with dry filler powder, and cen- 35 trifugally projecting said shot against the porous wood surface at velocities of from 3,000to 10,000

lineal feet per minute to deposit and hammer said filler into said surface pores.

7. The method of filling the surface pores of porous wood which includes, selecting spherical the surface pores.

8. The method of nlling the surface pores of porous wood which includes, selecting spherical shot having a diameter of from .040 inch to .005 inch, coating said shot with a dry filler powder,

. and centrifugally projecting said shot against the porous wood surface at velocities of from 3,000 to 10,000 lineal feet per minute to calk said filler into the surface pores; I

9. The method of filling the surface pores of porous wood which includes, mixing a selected dry coloring material with dry filler powder, coat.-

ing. spherical shot with said filler-coloring material mixture, and projecting the dry mixture coated shot against the porous wood surface to filler powder in proportions such as to match the calk said filler into the surface pores andstain the wood surface. I I

10. The method of filling the porous wood which includes, selecting spherical shot having a diameter of from .040 inch 'to..065'

inch, mixing a selected coloring pigment and a surface pores of; 

